We all know the ingredients of a perfect wedding: Something old, something new, something borrowed, something blue. But what you might not know is if your choice for something blue is the Caribbean Sea, you can save something green--as in thousands of dollars on wedding costs.

According to Bride's Magazine, the average cost of a wedding ranges between $20,000 and $30,000 depending on your location, and that doesn't include the honeymoon. Of course, there are always cheaper options if you remove all the pomp and circumstance from the picture. Renting a chapel and eloping in Vegas, e.g., can run you as little as a few hundred dollars (only $35 for the license)--but what it may cost you in friends and family relations could be a bit steeper.

There is a happy medium: getting married on a cruise ship. After doing the math, we found that couples can save upwards of $15,000 on their wedding day if they get hitched at sea. Even on a luxury liner, for seven nights and guests included, the total bill is only a fraction of what getting married the old-fashioned way is expected to cost.

But Pat Webb, president of GalaxSea Cruises and Tours, admits shipboard nuptials are not for everyone. "If you're getting married for the second or third time, they're great because you'll invite less people. But first-time wedders, who want all their friends and family there, will end up spending more [than on a conventional wedding] if everyone gets a cruise ticket."

Different cruise lines appeal to different marrying folk. Some are best for privacy seeking twosomes (geared toward the renewers or serial "been there, done that" brides and grooms). Others accommodate entire wedding parties--briefly. Guest come aboard at the ship's embarkation point for a one-day ceremony and leave before the newlyweds set sail. There are even programs for those who wish to renew their vows.

Carnival Cruise Lines

Carnival wants to give lovebirds more, ahem, bang for their buck, offering the cheapest combination wedding and honeymoon getaway deals. 2,200 couples are expected to have partaken in a Carnival wedding on its Glory line by the end of this year. Although it certainly has enough lounge spaces for full-blown receptions, glitzy Carnival (aka the "fun ship") is often more the choice for elopers given its reputation for being a floating Las Vegas.

"Just for the Bride and Groom" runs $750 and includes an official civil ceremony, champagne toasts and flutes, flowers for both newlyweds, a two-tiered wedding cake, music and photo ops. Couples either use Carnival's on-board officiant or bring their own religion-specific clergy along.

Those who want a private reception, more bubbly, more photos, or live music, pay about twice as much.

Total cost? Plan on spending upwards of $2,000 for the deluxe package as Carnival's weeklong Caribbean cruises tend to average about $529. Those who bring guests, let's say 10, still end up paying less than $10,000 in full. Visit carnival.com/ or call 888/CARNIVAL for more info.

Windjammer Barefoot Cruises

Tall, dark, and handsome. I'm talking about Windjammer ships, not the groom, silly. Windjammer has a unique fleet comprised of restored tall-masted schooners (the kind Ahab used to whale hunt). Its boats, often powered by the wind, can sail into hideaway coves the larger cruise ships cannotthese cruisers carry 120 or so total versus thousands on board Carnival or other biggies. It's a more intimate setting that can serve as an ideal venue for a more private alternative to the altar. Here's the deal (cutely named after tropical flora); only Carnival is cheaper.